Fiber optic cable breakout configuration with excess fiber length

ABSTRACT

The present disclosure relates to a telecommunications cable including a distribution cable and a tether that braches from the distribution cable at a mid-span breakout location. A flexible closure covers the mid-span breakout location. Within the closure, fibers are broken out from the distribution cable and spliced to fibers of the tether. The lengths of broken out fibers within the flexible closure are provided with sufficient excess fiber length to allow the closure to be readily bent/flexed in any direction without damaging the fibers.

RELATED APPLICATION

This application claims benefit of provisional application Ser. No.60/781,280, entitled FIBER OPTIC CABLE BREAKOUT CONFIGURATION, filedMar. 9, 2006, the disclosure of which is incorporated by reference.

TECHNICAL FIELD

The principles disclosed herein relate to fiber optic cable systems.More particularly, the present disclosure relates to fiber optic cablesystems having main cables and branch cables.

BACKGROUND

Passive optical networks are becoming prevalent in part because serviceproviders want to deliver high bandwidth communication capabilities tocustomers. Passive optical networks are a desirable choice fordelivering high-speed communication data because they may not employactive electronic devices, such as amplifiers and repeaters, between acentral office and a subscriber termination. The absence of activeelectronic devices may decrease network complexity and/or cost and mayincrease network reliability.

FIG. 1 illustrates a network 100 deploying passive fiber optic lines. Asshown in FIG. 1, the network 100 may include a central office 110 thatconnects a number of end subscribers 115 (also called end users 115herein) in a network. The central office 110 may additionally connect toa larger network such as the Internet (not shown) and a public switchedtelephone network (PSTN). The network 100 may also include fiberdistribution hubs (FDHs) 130 having one or more optical splitters (e.g.,1-to-8 splitters, 1-to-16 splitters, or 1-to-32 splitters) that generatea number of individual fibers that may lead to the premises of an enduser 115. The various lines of the network can be aerial or housedwithin underground conduits (e.g., see conduit 105).

The portion of network 100 that is closest to central office 110 isgenerally referred to as the F1 region, where F1 is the “feeder fiber”from the central office. The F1 portion of the network may include adistribution cable having on the order of 12 to 48 fibers; however,alternative implementations may include fewer or more fibers. Theportion of network 100 that includes an FDH 130 and a number of endusers 115 may be referred to as an F2 portion of network 100. Splittersused in an FDH 130 may accept a feeder cable having a number of fibersand may split those incoming fibers into, for example, 216 to 432individual distribution fibers that may be associated with a like numberof end user locations.

Referring to FIG. 1, the network 100 includes a plurality of breakoutlocations 125 at which branch cables (e.g., drop cables, stub cables,etc.) are separated out from main cables (e.g., distribution cables).Breakout locations can also be referred to as tap locations or branchlocations and branch cables can also be referred to as breakout cables.At a breakout location, fibers of the branch cables are typicallyspliced to selected fibers of the main cable. However, for certainapplications, the interface between the fibers of the main cable and thefibers of the branch cables can be connectorized.

Stub cables are typically branch cables that are routed from breakoutlocations to intermediate access locations such as a pedestals, dropterminals or hubs. Intermediate access locations can provide connectorinterfaces located between breakout locations and subscriber locations.A drop cable is a cable that typically forms the last leg to asubscriber location. For example, drop cables are routed fromintermediate access locations to subscriber locations. Drop cables canalso be routed directly from breakout locations to subscriber locationshereby bypassing any intermediate access locations

Branch cables can manually be separated out from a main cable in thefield using field splices. Field splices are typically housed withinsealed splice enclosures. Manual splicing in the field is time consumingand expensive.

As an alternative to manual splicing in the field, pre-terminated cablesystems have been developed. Pre-terminated cable systems includefactory integrated breakout locations manufactured at predeterminedpositions along the length of a main cable (e.g., see U.S. Pat. Nos.4,961,623; 5,125,060; and 5,210,812). However, the installation ofpre-terminated cables can be difficult. For example, for undergroundapplications, pre-terminations can complicate passing pre-terminatedcable through the underground conduit typically used to hold fiber opticcable (e.g., 1.25 inch inner diameter conduit). Similarly, for aerialapplications, pre-terminations can complicate passing pre-terminatedcable through aerial cable retention loops.

SUMMARY

Certain aspects of the disclosure relate to mid-span breakoutconfigurations for pre-terminated fiber optic distribution cables.

A variety of additional inventive aspects will be set forth in thedescription that follows. The inventive aspects can relate to individualfeatures and to combinations of features. It is to be understood thatboth the forgoing general description and the following detaileddescription are exemplary and explanatory only and are not restrictiveof the broad inventive concepts upon which the embodiments disclosedherein are based.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a prior art passive fiber optic network;

FIG. 2 is a cross sectional view of an example distribution cable;

FIG. 3 is a side view of a mid-span breakout location having featuresthat are examples of inventive aspects in accordance with the principlesof the present disclosure;

FIG. 4 is a left end view of the mid-span breakout location of FIG. 3;

FIG. 5 is a right end view of the mid-span breakout location of FIG. 3;

FIG. 6 is a side view of the mid-span breakout location of FIG. 3 withthe overmold removed;

FIG. 7 is a side view of the mid-span breakout location of FIG. 3 withthe overmold and protective sleeve removed;

FIG. 7A is a cross sectional view taken along section line 7A-7A of FIG.7;

FIG. 7B is a cross sectional view taken along section line 7B-7B of FIG.7;

FIG. 8 is a cross sectional view of the tether taken along section line8-8 of FIG. 7;

FIG. 9 is a perspective view of a base of a retention block used at themid-span breakout location of FIG. 3;

FIG. 10 is a front side view of the base of FIG. 9;

FIG. 11 is a top view of the base of FIG. 9;

FIG. 12 is a bottom view of the base of FIG. 9;

FIG. 13 is a left end view of the base of FIG. 9;

FIG. 14 is a right end view of the base of FIG. 9;

FIG. 15 is a perspective view of a cover adapted to mount to the base ofFIG. 9;

FIG. 16 is a top view of the cover of FIG. 15;

FIG. 17 is a front side view of the cover of FIG. 15;

FIG. 18 is an underside view of the cover of FIG. 15;

FIG. 19 is a right end view of the cover of FIG. 15;

FIG. 20 is a perspective view of a splice stiffener used at the mid-spanbreakout location of FIG. 3;

FIG. 21 is a front side view of the splice stiffener of FIG. 20;

FIG. 22 is a top view of the splice stiffener of FIG. 20;

FIG. 23 is a bottom view of the splice stiffener of FIG. 20;

FIG. 24 is a right end view of the splice stiffener of FIG. 20;

FIG. 25 is a cross sectional view taken along section line 25-25 of FIG.22;

FIG. 26 is a cross sectional view taken along section line 26-26 of FIG.21, the splice stiffener is shown mounted on a distribution cable;

FIG. 27 is a perspective view of a stiffener used at the mid-spanbreakout location of FIG. 3;

FIG. 28 is a front side view of the stiffener of FIG. 27;

FIG. 29 is a cross sectional view taken along section line 29-29 of FIG.28;

FIG. 30 is a cross sectional view taken along section line 30-30 of FIG.28;

FIG. 31 is a perspective view of a protective sleeve used at themid-span breakout location of FIG. 3;

FIG. 32 is a front side view of the protective sleeve of FIG. 31;

FIG. 33 is a right end view of the protective sleeve of FIG. 31;

FIG. 34 is a left end view of the protective sleeve of FIG. 31;

FIG. 35 is a top view of the protective sleeve of FIG. 31;

FIG. 36 is a cross sectional view taken along section line 36-36 of FIG.32;

FIG. 37 is a cross sectional view taken along section line 37-37 of FIG.32;

FIG. 38 is a perspective view of a retention clip used to retain theprotective sleeve of FIG. 31 at the mid-span breakout location of FIG.3;

FIG. 39 is a front side view of the retention clip of FIG. 38;

FIG. 40 is a top view of the retention clip of FIG. 38;

FIG. 41 is a bottom view of the retention clip of FIG. 38;

FIG. 42 is a right end view of the retention clip of FIG. 38;

FIG. 43 is a side view of an overmold used at the mid-span breakoutlocation of FIG. 3;

FIG. 44 is a top view of the overmold of FIG. 43;

FIG. 45 is a bottom view of the overmold of FIG. 43;

FIG. 46 is a left end view of the overmold of FIG. 43;

FIGS. 47 and 48 are schematic views showing a method for providingexcess fiber length at the mid-span breakout location of FIG. 3;

FIG. 49 is a schematic view showing a distribution cable bent along a 90degree curve at a maximum bend radius;

FIG. 50 shows a first preparation step for a tether used at the mid-spanbreakout location of FIG. 3;

FIG. 51 shows a subsequent preparation step of the tether of FIG. 50;and

FIG. 52 shows an initial preparation of the distribution cable at themid-span breakout location;

FIG. 53 is a perspective view of an example mid-span breakout assembly;

FIG. 54 is a perspective view of an example retention block;

FIG. 55 is a perspective view of a base of the retention block of FIG.54;

FIG. 56 is a top view of the base of FIG. 55;

FIG. 57 is a bottom perspective view of the base of FIG. 55;

FIG. 58 is a side view of the base of FIG. 55;

FIG. 59 is a transverse cross-sectional view of the base of FIG. 55;

FIG. 60 is a front view of the base of FIG. 55;

FIG. 61 is a top perspective view of a cover of the retention block ofFIG. 54;

FIG. 62 is a bottom perspective view of the cover of FIG. 61;

FIG. 63 is a side view of the cover of FIG. 61;

FIG. 64 is a top view of the cover of FIG. 61;

FIG. 65 is a transverse cross-sectional view of the cover of FIG. 61;

FIG. 66 is a front view of the cover of FIG. 61;

FIG. 67 is a top view of the cover of FIG. 61 showing preparation of atether cable at an example mid-span breakout location;

FIG. 68 is a front perspective view of an example separation block;

FIG. 69 is a front perspective view of an example first section of theseparation block of FIG. 68;

FIG. 70 is a rear perspective view of the first section of FIG. 69;

FIG. 71 is a side view of the first section of FIG. 69;

FIG. 72 is a top view of the first section of FIG. 69;

FIG. 73 is a rear view of the first section of FIG. 69;

FIG. 74 is a rear perspective view of an example second section of theseparation block of FIG. 68;

FIG. 75 is a front perspective view of the second section of FIG. 74;

FIG. 76 is a side view of the second section of FIG. 74;

FIG. 77 is a top view of the second section of FIG. 74;

FIG. 78 is a cross-sectional view of the first section of FIG. 74; and

FIG. 79 is a side view of the second section of FIG. 74 showingpreparation of a distribution cable at an example mid-span breakoutlocation.

DETAILED DESCRIPTION

The present disclosure relates to mid-span breakout arrangementsprovided on distribution cables. A typical distribution cable includes arelatively large number of fibers (e.g., 72, 144 or more fibers). Thefibers are typically segregated into separate groups with each groupcontained within a separate buffer tube. The fibers within each buffertube can include either ribbon fibers or loose fibers.

For example, FIG. 2 shows an example distribution cable 220 includingsix separate buffer tubes 222 each containing twelve fibers 224. Thebuffer tubes 222 may be gel filled. The distribution cable 220 alsoincludes a central strength member 226 for reinforcing the cable 220,and an outer strength member 228 such as Kevlar for also reinforcing thecable. The distribution cable 220 further includes an outer jacket 230that encloses the buffer tubes 222. Ripcords 232 can be provided forfacilitating tearing away portions of the jacket 230 to access thefibers 224 within the jacket 230.

While distribution cables typically have a large number of fibers, thevarious aspects of the present disclosure are also applicable todistribution cables having fewer numbers of fibers (e.g., 2 or morefibers). For example, the distribution cable can include an outer jacketenclosing a single buffer tube and at least two strength membersextending on opposite sides of the single buffer tube. An outer strengthmember such as Kevlar can surround the single buffer tube within thejacket. The single buffer tube can enclose loose fibers or ribbonfibers.

A typical mid-span breakout location is provided at an intermediatepoint along the length of a distribution cable. Commonly a tether (e.g.,a drop cable or a stub cable) branches out from the distribution cableat the breakout location. The tether most commonly has a fewer number offibers as compared to the number of fibers provided within thedistribution cable. In an example embodiment, the tether has no morethan twelve fibers. The tether includes fibers that extend between firstand second ends. The first ends of the tether fibers are preferablyspliced to selected fibers of the distribution cable at the breakoutlocation. The second ends of the tether fibers can either beconnectorized or unconnectorized.

FIGS. 3-7 illustrate a mid-span breakout assembly 240 having featuresthat are examples of inventive aspects in accordance with the principlesof the present disclosure. The breakout assembly is positioned at amid-span breakout location 241. As shown at FIGS. 3, 6 and 7, a tether242 branches outwardly from a main distribution cable 220 at themid-span breakout location 241. The breakout location 241 is shownincluding a splice location 244 where selected fibers 224 _(dc) of themain distribution cable 220 (e.g., typically less than twelve fibers)are spliced to corresponding fibers 224 _(t) of the tether 242. Thebreakout assembly includes a splice sleeve 246 positioned over thesplices, and a splice stiffener 248 for holding the splice sleeve 246.The breakout assembly 240 also includes stiffeners 250 ₁, 250 ₂ betweenwhich the splice stiffener 248 is positioned. The fibers 224 _(dc) fromthe distribution cable 220 pass through the stiffener 250 ₁ to reach thesplice location 244. The fibers 224 _(t) from the tether 242 passthrough the stiffener 250 ₂ to reach the splice location 244. Thebreakout assembly 240 further includes a protective sleeve 252 (e.g., ashell) that covers the breakout location 241. The stiffeners 250 ₁, 250₂ and the splice stiffener 248 are all enclosed within the sleeve 252. Afirst end 254 of the sleeve 252 forms a tapered nose, and a second end256 of the sleeve 252 overlaps a retention block 258 through which thefibers 224 _(t) of the tether 242 pass. Retention clips 243 are used tosecure the protective sleeve 252 to the distribution cable 220. Thebreakout assembly 240 also includes an over-mold 260 that encloses andseals the protective sleeve 252, the clips 243 and the retention block258. In certain embodiments, a wrap of heat resistant tape 263 canprovide an intermediate layer between the protective sleeve 252 and theover-mold 260.

Referring to FIG. 8, the tether 242 joined to the distribution cable 220at the breakout location 241 is depicted as having a flat cableconfiguration. The flat cable configuration includes a central buffertube 262 containing a plurality of fibers 224 _(t) (e.g., typically oneto twelve loose or ribbonized fibers). Strength members 264 (e.g.,flexible rods formed by glass fiber reinforced epoxy) are positioned onopposite sides of the central buffer tube 262. An outer jacket 266surrounds the strength members 264 and the buffer tube 262. The outerjacket 266 includes an outer perimeter having an elongated transversecross-sectional shape. An additional strength layer 265 (e.g., Kevlar)can be positioned between the buffer tube 262 and the outer jacket 266.As shown at FIG. 8, the transverse cross-sectional shape includesoppositely positioned, generally parallel sides 268 interconnected byrounded ends 270.

When the tether 242 is secured to the distribution cable 220, the tether242 should preferably be able to withstand a pullout force of at least100 pounds. To meet this pullout force requirement, the retention block258 is used to strengthen the mechanical interface between the tether242 and the distribution cable 220. As shown at FIG. 7, the retentionblock 258 includes a base 280 and a cover 282 between which the tether242 extends. In one embodiment, the retention block 258 has a plasticconstruction.

Referring to FIGS. 9-14, the base 280 of the retention block 258includes a first end 284 positioned opposite from a second end 286. Thebase 280 is elongated along a length A that extends between the firstand second ends 284, 286. The base also includes a first side 288adapted to engage the outer surface of the distribution cable jacket,and a second side 290 adapted to engage the tether 242. The first side288 has a channel 292 that extends along the length L of the base 280.The channel 292 has a transverse cross-sectional shape that is curved tomatch the outer diameter of the distribution cable jacket 230. Thus,when the retention block 258 is mounted to the distribution cable 220,the distribution cable 220 nests within the channel 292 as shown atFIGS. 7A and 7B. The second side 290 of the base 280 includes aretention sleeve 294 defining an elongate opening 296 having atransverse cross-sectional shape that matches the transversecross-sectional shape of the outer perimeter of the tether cable jacket266. When the tether 242 is secured to the retention block 258, ajacketed portion of the tether 242 fits within the sleeve 294 (see FIG.7A). When the base is mounted on the distribution cable 220, the opening296 is elongated in a direction generally perpendicular to a radial lineB that extends outwardly from the center of the distribution cable 220.The second side 290 of the base 280 also includes a central groove 298 aand two side grooves 300 a. The grooves 298 a, 300 a are generallyparallel and extend along the length of the retention block 258. Thecentral groove 298 a is sized to receive the buffer tube 262 of thetether 242. The side grooves 300 a are sized to receive the strengthmembers 264 of the tether 242.

The base 280 also includes structures for resisting axial movementbetween the retention block 258 and the over-mold 260. For example, asshown at FIGS. 9-12, surface depressions 302 are provided adjacent thesecond end 286 of the base 280. The surface depressions 302 (e.g.,grooves, slots, cuts, notches, indentations) provide void regions forallowing over-mold material to fill-in during the over-molding processto provide a more secure connection between the retention block 258 andthe outer over-mold 260. In this way, a mechanical interlock is formedthat resists axial movement between the retention block 258 and theover-mold 260. In other embodiments, the base 280 can include outwardlyprojecting structures (e.g., flanges, bumps, ribs) that are embedded inthe over-mold to further resist axial movement between the over-mold andthe retention block.

The cover 282 of the retention block 258 mounts over the second side 290of the base 280 adjacent the first end 284 of the base 280. As shown atFIGS. 15-19, the cover 282 includes a central groove 298 b and two sidegrooves 300 b. When the cover 282 is mounted on the base 280, thecentral groove 298 b aligns with the central groove 298 a of the base280, and the side grooves 300 b align with the side grooves 300 a of thebase 280. Thus, when the retention block 258 is assembled, the buffertube 262 of the tether 242 is captured within the central grooves 298 a,298 b, and the strength members 264 of the tether 242 are capturedwithin the side grooves 300 a, 300 b (see FIG. 7B). An adhesive 299 (seeFIG. 7B) can be applied between the cover 282 and the base 280 tosecurely affix the tether 242 to the retention block 258. In oneembodiment, the adhesive 299 is applied to the second side 290 of thebase 280, the grooved side of the cover 282, the buffer tube 262 of thetether 242, and the strength members 264 of the tether 242.

The retention block 258 also includes structures for facilitatingaligning the cover 282 on the base 280. For example, as shown at FIG.7B, the retention block 258 can include mating posts 304 and holes 306provided on the cover 282 and the base 280. The posts 304 fit within theholes 306 to maintain alignment between the base 280 and the cover 282during assembly.

The retention block 258 further includes an outer band groove 308 (seeFIGS. 9 and 15) that extends around at least a portion of the perimeterof the retention block 258. The band groove 308 is sized to receive astrap or band 297 (see FIG. 7) that is wrapped around the retentionblock 258 and the distribution cable 220 to secure the retention block258 to the distribution cable 258. The band can also function to assistin holding the cover 282 on the base 280.

The splice stiffener 248 of the breakout assembly 240 preferably has acrush-resistant construction adapted to prevent the splices of thebreakout location 241 from being damaged. In one embodiment, the splicestiffener 248 is made of a plastic material. As shown at FIGS. 20-26,the splice stiffener 248 includes an elongated base portion 320 having agenerally half-cylinder shape. The base portion 320 includes first andsecond sides 322, 324 that face in opposite directions. The first side322 of the base portion 320 includes a concave surface 325 defining achannel 326 having an open side. When the splice stiffener 248 ismounted at the breakout location 241, the concave surface 325 is adaptedto face toward the buffer tubes 222 of the distribution cable 220. Asshown in the cross-sectional view of FIG. 26, the concave surface 325has a semi-circular shape having a curvature that generally matches anouter diameter D circumscribing the buffer tubes 322 of the distributioncable 320. The concave surface 325 is shown covering approximately onehalf the diameter D, and a plurality of the buffer tubes 222 are shownpositioned within the channel 326. Depending upon how the break-outlocation is prepared (i.e., whether or not the outer strength members228 of the distribution cable 220 have been removed), the layer formedby the strength members 228 may be positioned between the surface 325and the buffer tubes 222.

The splice stiffener 248 also includes a pair of parallel retainingmembers 328 that project outwardly from the second side 324 of the baseportion 320. A splice retention channel 330 having an open side isdefined between the retaining members 328. A bed 332 of the channel 330is generally planar. Splice sleeve retention ridges or shoulders 334project outwardly from the bed 332 adjacent opposite ends of the channel330. Snap fit tabs 336 project laterally into the channel 330 from theretaining members 328. In use, the splice sleeve 246 is snap fit betweenthe tabs 336 and into the channel 330. Once the splice sleeve 246 is inthe splice retention channel 330, the tabs 336 prevent the splice sleeve246 from unintentionally exiting the splice retention channel 330through the open side. Also, the retention shoulders 334 prevent thesplice sleeve 246 from sliding out of the splice retention channel 330through the ends of the splice retention channel 330. Preferably, thesplice sleeve 246 is free to slide back and forth between the shoulders334 within the channel 330.

The stiffeners 250 ₁, 250 ₂ of the breakout assembly 240 are preferablyconfigured to provide increased crush resistance to the protectivesleeve 252. In certain embodiments, the stiffeners 250 ₁, 250 ₂ have astiffer construction than the protective sleeve 252 and are made of aplastic material. Referring to FIGS. 27-30, the stiffeners 250 ₁, 250 ₂have a generally tubular configuration and each define a through-passage340 for receiving their respective fibers 224 _(dc) and 224 _(t). Thethrough-passages 340 preferably have large enough cross-sectional areasto allow the fibers 224 _(dc), 224 _(t) to freely slide therein when thebreakout location 241 is bent. Ends 342 of the passages 340 preferablyinclude contours that extend around the perimeter of the passages 340for preventing the fibers from being bent beyond acceptable bend radiusrequirements.

Referring to FIG. 30, the stiffeners 250 ₁, 250 ₂ each include a baseportion 344 spaced from an arcuate dome portion 346. The stiffeners 250₁, 250 ₂ each also include a pair of planar, generally parallel sidewalls 348 that connect the base portion 344 to the dome portion 346. Thebase portions 344 define concave channels 350 adapted to receive buffertubes 222 of the distribution cable 220 when the stiffeners 250 ₁, 250 ₂are positioned at the breakout location 241. The sidewalls 348 and thedome portion 346 define an exterior shape that generally matches theinterior shape of the protective sleeve 252.

The protective sleeve 252 of the mid-span breakout assembly 240 isadapted to form a protective shell over the breakout location 241. Theprotective sleeve 252 is preferably sufficiently flexible to allow thepre-terminated cable (i.e., the distribution cable 220 with the tethersterminated 242 thereto) to be readily stored on a spool. The stiffeners248, 250 ₁, 250 ₂ provide regions/segments of increased crush resistanceseparated by regions/segments of increased flexibility.

Referring to FIGS. 31-37, the protective sleeve 252 is elongated along alength that extends between the first end 254 and the second end 256 andhas a generally U-shaped transverse cross section forming a channel 360(see FIG. 36) with an open side sized to be inserted over thedistribution cable. The channel 360 has a cross sectional shape sized toconform generally with the outer cross sectional shape of the stiffeners250 ₁, 250 ₂. Preferably, the internal transverse cross sectional shapeof the channel 360 is sized to accommodate sufficient slack or excessfiber length to allow the breakout location 241 to be bent withoutnegatively affecting performance or damaging the fibers of the breakoutlocation. The channel 360 of the protective sleeve 252 is definedbetween opposing sidewalls 362 defining openings 364 for receivingsnap-fit tabs 366 of the retention clips 243. The sidewalls 362 areinterconnected by a curved portion 363.

The first end 254 of the protective sleeve 252 includes a low profileportion 365 that fits closely to the distribution cable 220. The lowprofile portion 365 includes a channel 367 that receives the outerjacket 230 of the distribution cable 220. The channel 367 has a diameterthat generally matches the outer diameter of the distribution cable 220.The first end 254 also includes a transition portion 369 that provides asmooth taper/contour between the low profile portion 365 and a main bodyof the protective sleeve 252. The low profile portion 365 and thetransition portion 369 cooperate to provide a smooth transition from thedistribution cable 220 to the main outer surface of the protectivesleeve 252. The smooth taper provided by the first end (i.e., theleading end/nose) of the protective sleeve 252 assists in pulling thecable through underground conduit without snagging the breakout location241. The second end 256 of the protective sleeve 252 forms an enlargedreceptacle 372 sized sufficiently large to receive the retention block258. A tapered transition portion 370 is provided between the main bodyof the protective sleeve 252 and the enlarged receptacle 372. When thesleeve 252 is mounted on the distribution cable 220, the low profileportion 365 overlaps the jacket 230 at the upstream end of the breakoutlocation and the enlarged receptacle 372 overlaps the retention blockadjacent the downstream end of the breakout location.

As shown at FIGS. 38-42, the retention clips 243 of the mid-spanbreakout assembly 240 include curved portions 380 that receive thedistribution cable 220 on the opposite side of the protective sleeve 252such that the distribution cable 220 is captured between the clips 243and the protective sleeve 252. The clips 243 also include straightextensions 382 that project upwardly from the curved portion 380. Theextensions 382 of the clips 243 fit inside the protective sleeve 252 andassist in preventing fibers 224 _(dc), 224 _(t) from being pinchedbetween the protective sleeve 252 and the distribution cable 220 or theclips 243. The extensions 382 include snap-fit tabs 366 that fit withinthe openings 364 of the protective sleeve 252. The clips 243 alsoinclude discrete stops 384 for engaging bottom edges of the protectionsleeve 252. The stops 384 are located at the exteriors of the clips 343and project outwardly from the curved portions 380.

The over-mold 260 of the mid-span breakout assembly 240 is preferablymade of a polymer plastic material. As shown at FIGS. 43-46, theover-mold 260 has a primary contour 390 at a leading edge configured tocoincide generally with the contour of the leading end of the protectivesleeve 252. A trailing end 392 of the over-mold 260 is also slightlycontoured. The transverse cross sectional shape of the over-moldincludes first and second curved portions 395, 396 interconnected bygenerally planar portions 397, 398.

It is preferred for the over-mold 360 to be sized with a cross sectionalshape sufficient to allow the breakout location to be readily passedthrough a one and one-half inch inner diameter conduit or a one andone-quarter inch diameter conduit. In certain embodiments, the breakoutlocation has a cross sectional area that can be passed through a oneinch inner diameter conduit.

The mid-span breakout location 241 is preferably configured to allow themid-span breakout location to be bent/flexed in any orientation withoutdamaging the fibers 224 _(dc), 224 _(t) and without significantlynegatively affecting cable performance. In one embodiment, thisflexibility is provided by making sure that the fibers 224 _(dc), 224_(t) have sufficient excess fiber length (i.e., slack) to allow thebreakout location to be bent/flexed the requisite amount. In oneembodiment, the fibers 224 _(dc), 224 _(t) that extend along themid-span breakout location 241 are provided with at least 2% excessfiber length. In other embodiments, the fibers 224 _(dc), 224 _(t) areprovided with at least 3% excess fiber length. In still otherembodiments, the fibers 222 _(dc), 224 _(t) are provided with an excessfiber length in the range of 1 to 5% or in the range of 2 to 5%. In oneexample embodiment, the length of the mid-span breakout location 241 isabout 32 centimeters and about 1 centimeter of excess fiber length isprovided to the fibers 224 _(dc), 224 _(t) as they extend along themid-span breakout location 241.

When the mid-span breakout assembly 240 is assembled, measures are takento provide the fibers 222 _(dc), 224 _(t) with excess fiber length. Forexample, after the fibers 222 _(dc), 224 _(t) have been fused together,the fibers 222 _(dc), 224 _(t) are pulled taut and the retention block258 is positioned against the outer jacket 230 of the distribution cable220 (see FIG. 47). The retention block 258 is then slid a distance Xalong the distribution cable 220 to the position of FIG. 48. With theretention block 258 in the position of FIG. 48, and adequate amount ofexcess slack/excess fiber length has been provided to the fibers 222_(dc), 224 _(t). Once the retention block 258 is in the position of FIG.48, a securement structure 297 (e.g., a band, strap, clamp or other typeof structure) is used to fix the retention block 258 in positionrelative to the distribution cable 220. Thereafter, the remainder of themid-span breakout assembly 240 can be assembled over the mid-spanbreakout location 241.

In determining the amount of excess fiber length to be provided at themid-span breakout location 241, it is desirable for the distributioncable 220 to be able to be bent in a minimum bend radius R_(m) in anyorientation without compromising the mid-span breakout assembly 240. Inone embodiment, an example minimum bend radius R_(m) is ten times theouter diameter of the distribution cable 220. When the distributioncable is flexed to a bend having a radius R_(m) as shown at FIG. 49, aportion 500 of the distribution cable 220 at the outside of the curveelongates and a portion 501 of the distribution cable at the inside ofthe curve shortens. The centerline of the distribution cable does notchange in length. Taking the above factors into consideration, theamount of slack fiber length required to accommodate the elongation atthe outer portion 500 of the bend can be calculated by the followingformula:

${{\alpha\;\frac{\pi}{180{^\circ}}\left( {R_{m} + R_{dc}} \right)} - {\alpha\;\frac{\pi}{180{^\circ}}R_{m}}} = {\alpha\;\frac{\pi}{180{^\circ}}R_{dc}}$

In the above formula, where R_(dc) equals the outer radius of thedistribution cable measured from the centerline to the outer surface ofthe outer jacket. R_(dc) provides a value that is representative of thedistance between the fibers 222 _(dc), 224 _(t) and the centerline ofthe distribution cable. The angle of the bend is represented in α indegrees. For a 90° bend, the excess fiber length equals at leastπR_(dc)/2. For a 180° bend, the excess fiber length equals πR_(dc).

To prepare the tether 242 to be incorporated into the mid-span breakoutassembly 240, a portion of the outer jacket 266 is stripped away toexpose the central buffer tube 262 and the strength members 264 (seeFIG. 50). As shown at FIG. 50, the central buffer tube 262 and thestrength members 264 project outwardly beyond an end 271 of the outerjacket 266. As shown at FIG. 50, the strength layer 265 has been removedfrom around the buffer tube 262. After removing the end portion of theouter jacket 266, the strength members 264 are trimmed as shown at FIG.51, and an end portion of the central buffer tube 262 is removed toexpose the fibers 224 _(t). The tether 242 is then mounted to the base280 of the retention block 258. For example, as shown at FIG. 51, thejacketed end 271 of the tether 242 is inserted into the retention sleeve294. Also, the strength members 264 are positioned within the sidegrooves 300 a of the base 280, and the central buffer tube 262 isinserted within the central groove 298 a of the base 280. As shown inFIG. 51, the central buffer tube 262 has a length that extends beyondthe first end 284 of the base 280, and the strength members 264 havelengths that terminate generally at the first end of the base 280.

To prepare the mid-span breakout location on the distribution cable 220,a portion of the outer jacket 230 is first stripped away to provide astripped region 400 having an upstream end 402 and a downstream end 404.Portions of a cable netting can then be removed adjacent the upstreamand downstream ends 402, 404 so that the buffer tubes 222 are exposed.The outer strength member 228 can also be displaced (e.g., bunched atthe bottom side of the cable) adjacent the ends 402, 404 to facilitateaccessing the buffer tubes 222. Tape 406 can be used to prevent theintermediate length of netting that remains at the mid-span breakoutlocation 241 from unraveling. One of the buffer tubes 222 is thenselected and a first window 408 is cut into the buffer tube adjacent theupstream end 402 of the stripped region 400 and a second window 410 iscut into the buffer tube 220 adjacent the downstream end 404 of thestripped region 400. The fibers 224 _(dc) desired to be broken out arethen accessed and severed at the second window 410. After the fibers 224_(dc) have been severed, the fibers 224 _(dc) are pulled from the buffertube 222 through the first window 408 (see FIG. 52). With thedistribution cable 220 prepared as shown in FIG. 52, the fibers 224_(dc) are ready to be terminated to the prepared tether 242 of FIG. 51.

To connect the tether 242 to the fibers 224 _(dc), the splice sleeve 246and the two stiffeners 250 ₁, 250 ₂ are first slid over the fibers 224_(t) of the tether and up against the retention block 258. In certainembodiments, the stiffeners 250 ₁, 250 ₂ and splice sleeve 246 can beconfigured to nest inside one another to minimize the space occupied bysuch components during the fusion process. In certain embodiments, thecomponents can be slid up over the buffer tube 262 of the tether 242.With the stiffeners 250 ₁, 250 ₂ and the splice sleeve 246 mounted onthe tether 242, the fibers 224 _(t) of the tether are fused to thefibers 224 _(dc) of the distribution cable 220. After the fusion processis complete, the splice sleeve 246 can be slid over the fusion locationto protect the splice. The fibers are then tested to confirm that thefibers meet minimum insertion loss requirements. After verifyinginsertion loss, the cover 282 can be adhesively bonded to the base 280of the retention block 258 to complete the assembly of the retentionblock.

Once the retention block 258 has been assembled, the retention block 258is used to pull the fibers 224 _(dc), 224 _(t) generally taut. With thefibers 224 _(dc), 224 _(t) pulled taut, the splice stiffener 248 ispositioned beneath the location of the splice sleeve 246 to ensure thatthe splice sleeve 246 is generally centered relative to the splicestiffener 248. The splice stiffener 248 can then be secured to thedistribution cable 220 with tape. Preferably, the splice stiffener 248is generally centrally located between the ends 402, 404 of the strippedregion 400 of the distribution cable 220.

After the positioning of the splice stiffener 248 has been determined,the retention block 258 is slid back along the distribution cable 220 toprovide the fibers 224 _(dc), 224 _(t) with sufficient excess fiberlength to allow bending of the mid-span access location. The retentionblock 258 is then affixed to the distribution cable 220.

Once the retention block 258 has been affixed to the distribution cable220, the stiffeners 250 ₁, 250 ₂ are preferably slid along the fibers224 _(dc), 224 _(t) to their appropriate stiffening positions. In apreferred embodiment, the stiffener 250 ₁ is placed generally at amidpoint between the upstream end 402 of the stripped region 400 and thesplice stiffener 248, and the stiffener 250 ₂ is positioned generally ata midpoint between the splice stiffener 248 and the downstream end 404of the stripped region 400. Once the stiffeners 250 ₁, 250 ₂ are inposition, the splice sleeve 246 can be snapped within the splicestiffener 248.

To finalize the assembly process, the protective sleeve 252 is securedover the stripped region 400 by the retention clips 243, and the heatresistant tape 263 is wrapped around the mid-span breakout location 241.Thereafter, the process is completed by applying the over mold 260 overthe taped mid-span breakout location. The over mold layer functions toseal and protect the underlying components of the mid-span breakoutassembly 240. Thereafter, the distribution cable 220 can be spooled. Itis preferred for the fibers 224 _(t) of the tether to be pre-terminatedto the fibers 224 _(dc) of the distribution cable. “Pre-terminated”means that the fibers 224 _(t) are fused or otherwise connected to thefibers 224 _(dc) of the distribution cable 220 at the factory as part ofthe cable manufacturing process rather than being field terminated. Theremainder of the mid-span breakout assembly is also preferably factoryinstalled.

Referring now to FIGS. 53-79, another example embodiment a mid-spanbreakout assembly 240′ is shown having features that are examples ofinventive aspects in accordance with the principles of the presentdisclosure. The mid-span breakout assembly 240′ includes a separationblock 700 located on an upstream end 402′ of a breakout location 241′and a retention block 600 located on a downstream end 404′ of thebreakout location 241′. The retention block 600 strengthens themechanical interface between the tether cable 242 and the distributioncable 220. The separation block 700 routes the optical fibers 224 _(dc)accessed from the buffer tube 222 of the distribution cable 220 to thesplice point with the tether cable 242. A tube 800 extends from theseparation block 700 to the retention block 600. The tube 800 protectsthe spliced optical fibers 224 _(dc), 224 _(t) along the length of thebreakout location 241′.

As shown in FIG. 54, the retention block 600 includes a base 610 and acover 650 between which the tether 242 extends. In one embodiment, theretention block 600 has a plastic construction. Referring to FIGS.55-60, the base 610 of the retention block 600 extends along a length A(FIG. 56) from a first end 620 to a second end 622. The base 610 alsoincludes a first side 626 (FIG. 57) adapted to engage the outer strengthmember 228 of the distribution cable 220, and a second side 628 (FIG.55) adapted to engage the tether 242. The base 610 includes a firstsection 605 and a second section 615 (FIG. 56). The first section 605 ofthe base 610 includes side surfaces 601, elongated along a length L,that extend from one end 622 of the base 610 to an intermediate end 621of the base 610. The second section 615 protrudes outwardly from theintermediate end 621 to the end 620 of the base 610.

The first side 626 of the base 610 has a channel 630 that extends alongthe length L of the first section 605 (FIG. 57). In some embodiments,the channel 630 has a transverse cross-sectional shape (FIG. 59) that iscurved to generally match the inner diameter of the distribution cablejacket 230. The channel 630 of the base 610 is configured to couple to astripped region of the distribution cable 220 (FIG. 53). In someembodiments, the channel 630 couples to the outer strength member 228 ofthe distribution cable. In one example embodiment, the outer strengthmember 228 includes multiple loose strands of Kevlar positioned aroundthe buffer tubes 222. Thus, when the retention block 600 is mounted tothe outer strength member 228, the outer strength member 228 and thebuffer tubes 222 of the distribution cable 220 nest within the channel630.

The second side 628 of the first section 605 of the base 610 includes acentral groove 602 and two side grooves 603, 604. The grooves 602-604are generally parallel and extend along the length L of the firstsection 605 of the base 610. A transverse cross-section of the firstsection 605 is shown in FIG. 59. The central groove 602 is sized toreceive the buffer tube 262 of the tether 242. The side grooves 603, 604are sized to receive the strength members 264 of the tether 242.

The second section 615 of the base 610 includes a transition flange 612that extends outwardly from the intermediate end 621 of the base 610. Insome embodiments, the transition flange 612 has a generally U-shapedtransverse cross-section. In one embodiment, the transition flange 612defines a groove 617 (FIG. 55).

The cover 650 of the retention block 600 mounts over the second side 628of the base 610. As shown at FIG. 64, the cover 650 includes a firstsection 655 and a second section 665. The cover 650 also includes afirst side 676 (FIG. 61) and a grooved side 678 (FIG. 62). The firstside 676 of the first section 655 includes a curved top surface 651extending from the intermediate end 671 to the first end 672. Atransition flange 662 having a generally U-shaped transversecross-section extends outwardly from the intermediate end 671 to asecond end 670. The grooved side 678 of the first section 655 of thecover 650 includes a central groove 652 and two side grooves 653, 654.

In use, the cover 650 is mounted onto the base 610 to align the centralgroove 652 of the cover 650 with the central groove 602 of the base 610,and to align the side grooves 653, 654 of the cover 650 with the sidegrooves 603, 604 of the base 610. Thus, when the retention block 600 isassembled, the buffer tube 262 of the tether 242 is captured within thecentral grooves 602, 652, and the strength members 264 of the tether 242are captured within the side grooves 603, 653, 604, 654 (FIG. 67). Anadhesive can be applied between the cover 650 and the base 610 tosecurely affix the tether 242 to the retention block 600. In oneembodiment, the adhesive is applied to the second side 628 of the base610, the grooved side 678 of the cover 650, the buffer tube 262 of thetether 242, and the strength members 264 of the tether 242.

In some embodiments, the retention block 600 also includes structuresfor facilitating aligning the cover 650 on the base 610. For example, asshown at FIGS. 55 and 62, the retention block 600 can include matingposts 668 and surface depressions (e.g., grooves, slots, cuts, notches,indentations) 608 provided on the cover 650 and the base 610. The posts668 fit within the notches 608 to maintain alignment between the base610 and the cover 650 during assembly. For example, in the embodimentshown, mating posts 668 protrude downwardly from the cover 650 to engagewith slots 608 on the side surfaces 601 of the base 610. In otherembodiments, however, other suitable alignment members could also beused.

Referring now to FIG. 67, to prepare the tether 242 to be incorporatedinto the mid-span breakout assembly 240′, a portion of the outer jacket266 of the tether cable 242 is stripped away to expose the centralbuffer tube 262 and the strength members 264. As shown at FIG. 67, thecentral buffer tube 262 and the strength members 264 project outwardlybeyond an end 271 of the outer jacket 266. The strength layer 265 hasbeen displaced from around the buffer tube 262. After removing the endportion of the outer jacket 266, the strength members 264 are trimmed asshown at FIG. 67, and an end portion of the central buffer tube 262 isremoved to expose the fibers 224 _(t).

The tether 242 is then mounted to the base 610 of the retention block600. For example, as shown at FIG. 67, the strength members 264 arepositioned within the side grooves 603, 604 of the base 610, and thecentral buffer tube 262 is inserted within the central groove 602 of thebase 610. The central buffer tube 262 has a length that extends beyondthe intermediate end 621 of the base 610, and the strength members 264have lengths that terminate generally at the intermediate end 621 of thebase 610. In some embodiments, the central buffer tube 262 extendsbeyond the end 620 of the retention block 600. In other embodiments,however, the central buffer tube 262 terminates between the intermediateend 621 and end 620.

Referring now to FIGS. 68-80, a separation block 700 provides supportfor transitioning fibers 224 _(dc) from the distribution cable 220 to afusion location. As shown in FIG. 68, the separation block 700 includesa Y-shaped housing 701 defining a first opening 711 on an upstream endof the separation block 700, a second opening 712 on a downstream end ofthe separation block, and a third opening 714 also located on thedownstream end. A generally tubular section 716 of the housing 701 formsthe first opening 711 and generally tubular sections 718, 719 of thehousing 701 form the second and third openings 712, 714.

The second opening 712 is generally aligned with the first opening 711to form a first channel 715 (FIGS. 71 and 76). The third opening 714leads to a second channel 717 (see FIGS. 71 and 76) that joins with thefirst channel 715 at the tubular section 716 of the housing 701. Tubularsections 716, 718 forming the first channel 715 are sized and shaped toenclose the buffer tubes 222 and central strength member 226 of thedistribution cable 220. Tubular section 719 forming the second channel717 is sized and shaped to fit within the tube 800 and to enclose thefibers 224 _(dc) accessed from the distribution cable 220 for splicingwith the fibers 224, of the tether cable 242.

In some embodiments, the separation block 700 is formed from a firstsection 710 and a second section 750. In the example shown, the firstand second sections 710, 750 each include grooves 715 a, 715 b thatalign and combine to form the channel 715. Similarly, aligning andcombining grooves 717 a, 717 b forms the channel 717. A protrudingsection 720 a defines the grooves 715 a, 717 a and a protruding section720 b defines the grooves 715 b, 717 b.

In some embodiments, the first and second sections 710, 750 are fastenedtogether with complementary surface depressions 722 and protrusions 724(FIGS. 70 and 75). In one example embodiment, the protruding section 720a on the first section 710 defines a hole 722 and the protruding section720 b on the second section 750 includes a protrusion 724 sized to fitwithin the hold 722. Adhesive can also be used to secure the firstsection 710 to the second section 750.

The mid-span breakout location on the distribution cable 220 can beprepared in a similar manner to the preparation discussed above withrespect to FIG. 52. A portion of the outer jacket 230 of thedistribution cable 220 is first stripped away to provide a strippedregion 400′ (FIG. 53). One of the buffer tubes 222 is selected and afirst window 408′ and a second window are cut into the selected buffertube 222. The fibers 224 _(dc) desired to be broken out are thenaccessed, severed, and pulled from the buffer tube 222 through the firstwindow 408′. With the distribution cable 220 prepared as shown in FIG.80, the severed fibers 224 _(dc) are ready to be fused with the tetherfibers 224 _(t).

To connect the tether 242 to the fibers 224 _(dc), the splice sleeve 246and the tube 800 (FIG. 53) are first slid over the fibers 224 _(t) ofthe tether 242, and the tube 800 is further slid up over the tetherjacket 266. With the splice sleeve 246 and tube 800 mounted on thetether 242, the fibers 224 _(t) of the tether are fused to the fibers224 _(dc) of the distribution cable 220. The fibers are then tested toconfirm that the fibers meet minimum insertion loss requirements.

After the fusion process is complete, the splice sleeve 246 can be slidover the fusion location to protect the splice. In some embodiments, thesplice sleeve 246 has a length of less than 40 mm. Preferably, thesplice sleeve 246 has a length of less than 35 mm. In one exampleembodiment, the splice sleeve 246 has a length of about 30 mm.Decreasing the length of the splice sleeve 246 increases the degree towhich the mid-span breakout assembly can bend. Increasing theflexibility of the breakout assembly 240, 240′ facilitates wrapping thedistribution cable 220 having the breakout assembly 240, 240′ around aspool.

After verifying the insertion loss, the tube 800 can be slid over thesplice sleeve 246 and the fusion location to protect the spliced fibers224 _(dc), 224 _(t). The separation block 700 can then be added to theupstream location 402′ of the stripped portion 400′ of the distributioncable 220. The buffer tubes 222 are routed through the first channel 715of the separation block 700 and the severed fibers 224 _(dc) are routedthrough the second channel 717 of the separation block 700 (FIG. 80). Toroute the fibers, in some embodiments, the buffer tubes 222 are laidwithin the first groove 715 a of the first section 710 of the separationblock 700 and the fibers 224 _(dc) are laid within the second groove 717a of the first section 710 as shown in FIG. 79. The second section 750of the separation block 700 can be secured to the first section asdiscussed above.

Typically, the separation block 700 does not enclose the outer strengthmember 228. In some embodiments, the outer strength member 228 can beredistributed uniformly about the buffer tubes 222 of the distributioncable 220 at the upstream and downstream ends 402′, 404′ afterinstalling the separation block 700. In such embodiments, the outerstrength member 228 extends across the breakout location 241′.

After installing the separation block 700, the tube 800 can be slid ontosection 719 of the separation block 700. In some embodiments, the tube800 can optionally be taped or otherwise temporarily secured to theseparation block 700. In other embodiments, the tube 800 is permanentlysecured to the separation block 700 with adhesive. In still otherembodiments, the tube 800 is not secured to the separation block 700.

The retention block 600 is then mounted to the tether cable 242. Theretention block 600 is preferably positioned so that one end of the tube800 is slid over the transition flanges 612, 662 of the retention block600 and the other end of the tube 800 remains over section 719 of theseparation block 700. In general, the tube 800 has an appropriate lengthto provide the fibers 224 _(dc), 224 _(t) with sufficient excess fiberlength to allow bending of the mid-span access location 241′. Theretention block 600 is then affixed to the distribution cable 220. Insome embodiments, the groove 630 of the base 610 of the retention blockis affixed (e.g., with adhesive) to the outer strength member 228wrapped around the distribution cable 220.

To finalize the assembly process, the heat resistant tape/foil can bewrapped around the mid-span breakout location 241′. Thereafter, theprocess is completed by applying an over mold 260′ over the mid-spanbreakout location 241′. The over mold layer 260′ functions to seal andprotect the underlying components of the mid-span breakout assembly240′. Thereafter, the distribution cable 220 can be spooled. It ispreferred for the fibers 224 _(t) of the tether to be pre-terminated tothe fibers 224 _(dc) of the distribution cable. The remainder of themid-span breakout assembly 240′ is also preferably factory installed.

As used herein, with respect to buffer tubes, the term “fiber accesslocation” can be any type of location where a fiber can be routed out ofa buffer tube. Example fiber access locations include windows, ring cutregions, or other openings in a buffer tube. Additionally, when thefibers 224 _(dc), 224 _(t) have been spliced together, the fibers 224_(dc), 224 _(t) can collectively be referred to as an optical fiberstructure. In such a case, the optical fiber structure includes a firstlength of optical fiber within the distribution cable, a second lengthof optical fiber that extends through the breakout location and a thirdlength of optical fiber that extends through the tether. The first,second and third lengths are in optical communication with one anotherso as to define a signal path that extends from the distribution cable,through the breakout location, to the end of the tether. The termoptical fiber structure also includes lengths of optical fibers that donot include intermediate splices. As used herein, the term “breakoutportions” of optical fiber include portions of optical fiber that extendalong the length of a breakout location.

From the forgoing detailed description, it will be evident thatmodifications and variations can be made in the devices of thedisclosure without departing from the spirit or scope of the invention.

1. A telecommunications cable comprising: a distribution cable includinga cable jacket and a plurality of buffer tubes positioned within thecable jacket, the plurality of buffer tubes including a first buffertube, the distribution cable including a mid-span location where aportion of the cable jacket has been removed and where at least thefirst buffer tube includes a fiber access location; a flexible closurethat surrounds the distribution cable and covers the mid-span location,the closure being factory installed, the closure being elongated along alength that extends along the distribution cable; a tether that branchesfrom the distribution cable at the closure, the tether including atether jacket, a tether buffer tube positioned within the jacket and atleast one strength member; a tether retention block affixed to thedistribution cable, the tether buffer tube passing through the retentionblock and at least the strength member of the tether being affixed tothe retention block; a first optical fiber that extends through thefirst buffer tube of the distribution cable, the first optical fiberbeing routed out of the first buffer tube through the fiber accesslocation; a second optical fiber that extends through the tether buffertube, the second fiber being routed into the flexible closure; the firstoptical fiber being spliced to the second optical fiber at a splicelocation located within the flexible closure; and the first opticalfiber including a breakout portion that extends from the fiber accesslocation to the splice location and the second optical fiber including abreakout portion that extends from the tether retention block to thesplice location, the breakout portions of the first and second fibershaving an excess fiber length of at least παR_(dc)/180°, wherein R_(dc)equals a radius of the distribution cable measured from a centerline ofthe distribution cable to an outer surface of the cable jacket and αequals a bend angle of the distribution cable.
 2. The telecommunicationscable of claim 1, wherein the excess fiber length is at least 3 percentof a combined length of the first and second optical fibers.
 3. Thetelecommunications cable of claim 1, wherein the excess fiber length isin the range of 2-5 percent of a combined length of the first and secondoptical fibers.
 4. The telecommunications cable of claim 1, wherein thetelecommunications cable is sized to be pulled through a conduit havinga 1.25 inch inner diameter.
 5. The telecommunications cable of claim 1,wherein the tether is a stub cable or a drop cable.
 6. Thetelecommunications cable of claim 1, wherein the flexible closureincludes an overmold.
 7. The telecommunications cable of claim 6,wherein the flexible closure includes an elongated protective sleevethrough which the breakout portions of the first and second fibers pass,the protective sleeve being encased within the overmold.
 8. Thetelecommunications cable of claim 7, further comprising stiffenerspositioned within the protective sleeve, the stiffeners being spacedapart along a length of the protective sleeve, the stiffeners providingthe protective sleeve with first regions of increased crush resistanceseparated by second regions having lesser degrees of crush resistancethan the first regions.
 9. The telecommunications cable of claim 8,wherein the stiffeners are separate pieces from the protective sleeve.10. The telecommunications cable of claim 8, wherein at least some ofthe stiffeners nest within the protective sleeve and have shapes thatengage and complement an interior of the protective sleeve.
 11. Thetelecommunications cable of claim 8, wherein the breakout portions ofthe first and second fibers extend through openings defined by thestiffeners.
 12. The telecommunications cable of claim 1, furthercomprising a splice sleeve for enclosing the splice location and asplice stiffener for holding the splice sleeve.
 13. Thetelecommunications cable of claim 12, wherein the splice sleeve canslide back and forth along a length of the splice stiffener.
 14. Thetelecommunications cable of claim 12, wherein the splice stiffenerincludes a base defining a channel having a concave curvature, thechannel fitting over a plurality of the buffer tubes.
 15. Thetelecommunications cable of claim 1, wherein the retention block definesa first portion configured to mate with a second portion.
 16. Thetelecommunications cable of claim 15, wherein each portion of theretention block defines at least one half-channel configured tocooperate with the half-channel of the other portion to receive thestrength member of the tether.
 17. The telecommunications cable of claim16, wherein each portion of the retention block defines at least threehalf-channels configured to cooperate with the half-channels of theother portion to receive the second optical fiber and two strengthmembers of the tether.
 18. The telecommunications cable of claim 1,wherein the retention block defines a reduced diameter portionconfigured to protrude within an elongated protective sleeve.